It is known to use a circuit board assembly apparatus having at least one movable carriage, i.e., gantry beam, mounted via bearings on guide rails for movement in one direction over a printed circuit board, while at least one component gripping device is mounted on the movable carriage for movement along the carriage in another direction. This device allows x-y positioning of electronic components held in the gripping device relative to a printed circuit board. Such an assembly is shown, for example, in U.S. Pat. No. 5,002,448, the contents of which are incorporated herein by reference.
The gantry beam is driven by a servo control system. To optimize manufacturing efficiency when mounting components on printed circuit boards, it is desirable to position the components as quickly as possible relative to the circuit board. However, such high speed operation produces undesirable vibrations, oscillations, resonances and the like in the gantry beam.
A particular problem is caused by the fact that the natural resonance frequencies of the gantry beam end change as the gantry beam load changes as the gripping device carried by the movable carriage traverses the beam. Thus, traditional systems for compensating for resonances, such as electronic notch filtering, would be very difficult to use in a gantry beam positioning system since the notch frequency setting would have to vary with the position of the load along the beam.